Below is a map of surface observations and
the leading edge of a tropical air mass surging northward into the Ohio
Valley has been highlighted in red. Southerly winds behind the boundary
signify the continued northward transport of warm moist air.

From these reports, we see that
most stations in the tropical air mass generally exhibit relatively warmer
temperatures, with higher
dew point temperatures,
and winds generally out of the south.
Notice that on the other side of the red boundary, outside of this air
mass, surface conditions are much different, which indicates the presence
of an entirely different air mass.